Tuesday, February 7, 2017

Forecast Hits and Misses

Forecast post mortem's are an essential part of forecasting.  Sometimes they are painful.  Today's is probably a 5 on a pain scale from 1-10.

Let's first review the precipitation forecast issued in yesterday's blog post (Expectations Through Tomorrow Afternoon).  For the 24-hour period ending at 5 PM today, I called for:

1. 2-3 inches of water equivalent for Ben Lomond Peak, Powder Mountain, and Snowbasin, with potentially higher amounts for Ben Lomond Peak
2. 1-2 inches of water equivalent for upper Little Cottonwood (Alta Collins)

As of 4 PM (I'm writing this early, but it's pretty much over for precip through 5 PM except for maybe a snow shower or two) the totals since 5 PM yesterday are:

Ben Lomond Peak: 3.5" (based on snow water change since that's the only ob working)
Powder Mountain (Powder Mountain 2 Station): 2.17"
Snowbasin (Middle Bowl Station): 1.59"
Snowbasin (Boardwalk Station): 1.95"

That's not too bad, but the low numbers at Snowbasin are a bit of a bummer for me and related to the more rapid cutoff of precipitation than expected following warm-frontal passage.  Even this morning, I didn't think we would shut down that abruptly.

Now, where things get ugly is in the central Wasatch.  Alta-Collins recorded only 0.46" of water equivalent (and 5 inches of snow) since 5 PM yesterday.  That's not even close to my forecast and I can find little solace from other observations in the central Wasatch.  Basically, the forecast was a bust in the central Wasatch.  While partly related to the rapid cutoff following warm-frontal passage, precipitation rates were overdone even before that occurred.  I've seen Alta get skunked from this flow direction before, so it was a possibility.  I just never know when one can count on it.

Now let's talk about the winds.  Here we also have a mixed bag.  Ogden Peak and Mount Baldy are the two main sites I look at for ridge-top winds.  Ogden Peak got raked pretty good, with a long period of gusts over 74 mph and a peak gust of 94 mph.

Impressive, but I must confess that I thought they would top 100 today.

Mt. Baldy blew hard, but not near the top wind gusts for that location, with a peak gust of 76 mph.

I can never remember if that site sees it's highest winds in S-SSW flow rather than SW-W.  I'll have to do some sleuthing for future use.

Some other maximum gusts reported to MesoWest in the Wasatch Range include 79 at Powder Mountain, 66 at Snowbasin-Wildcat, 65 at the top of Park City, 92 at Canyons 9990, and 62 at Deer Valley - Mt. Baldy, and 61 at the top of Alta's Collins chair.

These winds disrupted lift operations at several resorts (although Alta seemed to be running most of the day, although I didn't look in the later half of the afternoon), however, they were not as high as I thought they would be.

Time to go home, lick the wounds, and get ready for another at bat.


  1. 4.22" water at Sundance, 3.55" water Provo canyon. http://www.wrh.noaa.gov/total_forecast/getprod.php?wfo=slc&sid=SLC&pil=PNS

    1. Yes, thanks for pointing that out. That makes the low amounts in most of the central Wasatch even more perplexing. It's not unusual for Alta to get less precipitation in a pattern like yesterdays, but the contrast was quite extreme.

  2. The real pain look like the next push that will also be warm & wet, assuming the models are in the ballpark. It's been a very different year than last, but above all, the warming last year starting in Feb killed us. Let's hope for a different outcome this season!